1. Field of the Invention
The present invention relates to a fuel injection controller of an internal combustion engine.
2. Description of Related Art
As a kind of a fuel injection controller performing fuel injection control by operating an injector of an internal combustion engine having an occlusion agent, which occludes nitrogen oxides (NOx) when an air fuel ratio of exhaust gas is lean and discharges the NOx when the air fuel ratio is rich, there is a proposed controller that makes an air fuel ratio of a gasoline engine rich temporarily when a quantity of NOx occluded in an occlusion agent becomes equal to or greater than a predetermined value to discharge the NOx from the occlusion agent and to perform reduction purification of the discharged NOx (for example, as described in JP-A-H06-108824). This controller performs retardation operation of ignition timing to inhibit torque fluctuation when the controller makes the air fuel ratio rich.
However, the degree of the retardation of the ignition timing is restricted from the viewpoint of maintaining a suitable combustion state of the gasoline engine. In the case of a diesel engine, retardation of injection timing may be performed to inhibit the torque fluctuation when the air fuel ratio is made rich. Also in this case, the degree of the retardation of the injection timing is restricted from the viewpoint of maintaining the suitable combustion state of the diesel engine. Since the combustion state of the diesel engine becomes unstable specifically during rich combustion, there is a possibility that misfire is caused by performing the retardation of the injection timing.